Fuse resistor



Dec. 27, 1960 HAYNMAN 2,966,649

FUSE RESISTOR Filed Nov. 5, 1958 INVENTOR. ALEXANDRE HAYNMAN BY W/f%/ATTO RNE Y FUSE RESISTOR Alexandre Haynman, Copenhagen-Vanlosa, Denmark,

assignor to International Resistance Company, Philadelphia, Pa., acorporation of Delaware Filed Nov. 3, 1958, Ser. No. 771,533

14 Claims. (Cl. 338-322) This invention relates to the construction of afuse resistor, and more particularly, to an improved construction for aresistor having a fusible connection between the resistor element and aterminal therefor.

In many electrical circuits, it is often desirable to have a resistorwhich when heated to a predetermined temperature because of anelectrical overload on the resistor, will electrically open up andthereby discontinue the flow of current through the circuit to protectthe other components in the circuit. Resistors heretofore used for thispurpose comprise either a wire wound resistor element which isconstructed to burn out at the predetermined temperature or a resistorincluding a fusible link which melts at the predetermined temperature toopen the resistor. However, such fuse resistors heretofore availablehave the disadvantages that they are complicated in construction so thatthey are difiicult and expensive to manufacture, and, more importantly,once they open up they cannot be reused but must be replaced withanother resistor.

it is therefore an object of this invention to provide a novelconstruction of a fuse resistor.

It is another object of this invention to provide a novel constructionof a fuse resistor which includes a fusible link which melts at apredetermined temperature to open the resistor.

It is still another object of this invention to provide a novelconstruction of a fuse resistor which can be applied to any desired typeof resistor element.

It is another object of this invention to provide a novel constructionof a fuse resistor which permits the resistor to be reused once it hasopened up.

It is still a further object of this invention to provide a fuseresistor which is simple in construction so as to be easily andinexpensively manufactured.

Other objects of this invention will appear hereinafter.

For the purpose of illustrating the invention there is shown in. thedrawings forms which are presently pre ferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

Figure l is a longitudinal elevational view of one embodiment of thefuse resistor of this invention.

Figure 2 is an end elevational view of the embodiment of the fuseresistor of this invention shown in Figure 1.

Figure 3 is an exploded perspective view of the embodiment of the fuseresistor of this invention shown in Figure 1.

Figure 4 is a longitudinal elevational view of another embodiment of thefuse resistor of this invention.

Figure 5 is an end elevational view of the embodiment of the fuseresistor of this invention shown in Figure 4.

Figure 6 is an exploded perspective view of the embodiment of the fuseresistor of this invention shown inFigure 4.

atent O Figure 7 is a perspective view of still another embodiment ofthe fuse resistor of the present invention.

Figure 8 is a sectional view taken along line 88. of Figure 7.

Referring to the drawings, Figures 1, 2, and 3 show one embodiment ofthe fuse resistor of this invention, generally designated by 10. Fuseresistor 10 comprises an electrical resistor element 12 having a pair ofconductive wire terminal leads 14 and 16 extending from the endsthereof. Resistor element 12 may be any one of the well known types ofresistors; for example, (1) a core of insulating material having awire.of an elece trical resistance metal helically wound thereon and a jacketor casing of an electrical insulating material surrounding the core andwire, or (2) a core of insulating material having a film of anelectrical resistance material, such as carbon or a metal, coated on thesurface of the core, and a casing or jacket of an electrical insulatingmaterial surrounding the core and the film, or (3) a molded body of anelectrical insulating plastic having particles of an electricalresistance material, such as carbon, dispersed therein, and a casing orjacket ofan electrical insulating material surrounding said molded body.No matter which of the well known types of electrical resistors is usedfor resistor element 12 the terminal leads 14 and 16 are electricallyconnected to the ends of the resistor. and extend through theprotective, insulating casing or jacket. A band 13 of an electricallyconductive metal fits tightly around resistor ele-.

ment 12. Band 18 has a pair of spaced, substantially parallel arms 2t]and 22 extending outwardly therefrom anda substantially U-shaped troughportion 24. between the arms 2t? and 22 with the open end of the Ufacingoutwardy. One of the terminal leads, such as lead 14, Is bent backover resistance element 12 and extends into trough 24. Trough 24 isfilled with a fusible metal 26- (Figure 2), such as solder, whichelectrically and mechanically connects terminal lead 14 to band 18.Fusible metal 26 is of a composition which will melt at thepredetermined temperature at which it is desired for the resistor toopen. The particular composition of a solder which will melt at adesired temperature can be found in any well known handbook or catalogon solders. A terminal member 28 of an electrically conductive metal issecured to band 18 and extends beyond the end of. resistor element 12.Terminal member 28 can either be an integral part of band 18 or securedthereto such as by brazing or welding. Although terminal member 28 canbe soldered to band 18, care should be taken to usea solder which willmelt at a higher temperature than the melting temperature of fusiblemetal 26. Although terminal member 28 is shown extending from the sameend of resistor element 12 as terminal lead 14 so that the fuse resistor16} is terminated at each end thereof, terminal member 28 may extendradially from the fuse resistor 10 or from the same end as terminal lead16. Also, although resistor element 12 is shown to be of circularcross-section with the terminal band 18 being of similar configuration,resistor element 12 can be of any 24 by the fusible metal 26. Thus thefuse resistor 10 can be manufactured easily and quickly so as to berelatively inexpensive.

In use, fuse resistor 10 is connected into the desired circuit throughterminal lead 16 and terminal member 28. Thus resistor element 12 isconnected in the circuit at one end through terminal lead 16 and at theother end through terminal lead 14, fusable metal 26, band 18, andterminal member 28. During normal operation of the circuit resistorelement 12 will heat up slightly but not to the melting point of fusablemetal 26. However, if the circuit becomes overloaded, resistor element12 will become overheated and when it reaches the melting pointtemperature of fusable metal 26, the fusable metal 26 will melt and theterminal lead 14 through its own resiliency will spring out of trough 24to open circuit the fuse resistor 10. This in turn cuts off the flow ofcurrent through the circuit and thereby protects the other components inthe circuit from becoming damaged by the overload of current. When thecause of the overload in the circuit has been corrected, and it isdesired to close the circuit, it is only necessary to press terminallead 14 back into trough 24 and reconnect it to band 18 by additionalfusable metal 26. Thus, it is not necessary to replace the fuse resistor10, as must be done with previously available fuse resistors, but thefuse resistor of this invention can be reused over again.

Figures 4, 5, and 6 show another embodiment of the fuse resistor of thisinvention, generally designated as 30. Fuse resistor 30 comprises a body32 of an electrical insulating material, such as a plastic or ceramic,having a pair of spaced holes 34 and 36 extending longitudinallytherethrough slightly beneath the surface thereof. Body 32 is also shownto have a central longitudinally extending hole 38 which can be used formounting the fuse resistor 30. A terminal lead 40 of an electricallyconductive metal fits tightly into hole 34 and projects beyond body 32from only one end thereof. A terminal lead 42 of an electricallyconductive metal fits in hole 36 and projects beyond body 32 from bothends thereof. Body 32 is provided adjacent its end from which terminallead 40 projects with a transverse slot 44 extending from the surface ofbody 32 to the hole 34 to expose a portion of terminal lead 40. A band46 of an electrically conductive metal fits tightly around body 32adjacent the other end of the body. Band 46 has a pair of spaced,substantially parallel arms 48 and 50 extending outwardly therefrom anda substantially U-shaped trough portion 52 between arms 48 and 50 withthe open end of the U facing outwardly. A wire 54 of an electricalresistance metal is helically wound around and along body 32. At one endwire 54 extends across and into slot 44 and contacts terminal lead 40.Wire 54 may be welded or soldered to terminal lead 40 to insure goodelectrical contact thereto. The other end of wire 54 is connected toband 46 such as by welding, soldering, or the like. The portion 42a ofterminal lead 42 which projects beyond the end of body 32 opposite theend of the body to which band 46 is secured is bent back over body 32and extends into trough 52. Trough 52 is filled with a fusable metal 56,such as solder, to electrically and mechanically connect terminal lead42 to band 46. If desired, body 32 and resistance wire 54 may beprovided with a protective, electrical insulating coating or jacket,leaving portion 42a of terminal lead 42 and trough 52 exposed. Althoughbody 32 is shown to be of elliptical cross-sectional configuration, itmay be of any desired cross-sectional con figuration, such asrectangular, circular, or the like. Also, although the resistancematerial is shown to be a metal Wire, it can also be a film of aresistance material, such as carbon or a metal, coated on the surface ofbody 32 and extending into slot 44 to contact terminal lead 40 as wellas contacting band 46. Fuse resistor 39 is used and operates in the samemanner as fuse resistor 10 previously described.

Figure 7 shows still another embodiment of the fuse resistor of thepresent invention, generally designated as 58. Fuse resistor 58comprises a body 60 of an electrical insulating material, such as aplastic or ceramic, having a pair of spaced holes 62 and 64 extendinglongitudinally therethrough slightly beneath the surface thereof, and acentral longitudinally extending hole 66. A terminal lead 68 of anelectrically conductive metal fits tightly into hole 62 and projectsbeyond one end of body 60. A wire member 70 of an electricallyconductive metal fits into hole 64 and projects beyond the other end ofbody 60, with the projecting end of the wire member 70 being bent backover the outer surface of the body 60. Body 60 is provided adjacent itsend from which terminal lead 68 projects with a transverse slot 72extending from the surface of body 60 to the hole 62 to expose a portionof the terminal lead 68. Body 60 is also provided adjacent its end fro-mwhich wire member 70 projects with a transverse slot 74 extending fromthe surface of the body 60 to the hole 64 to expose a portion of thewire member 74 A wire 76 of an electrical resistance metal is helicallywound around and along body 60. At one end wire 76 extends across andinto slot 72 and contacts terminal lead 68. At the other end wire 76extends across and into slot 74 and contacts wire member 70. Wire 76 maybe welded or soldered to terminal lead 68 and wire member 70 to insuregood electrical contact thereto. A second terminal lead 78 of anelectrical conducting metal extends through central hole 66 and projectsbeyond both ends of the body 69. The end 78a of the second terminal lead78 which projects from the same end of body 60 as the first terminallead 68 is bent back over the outer surface of body 6-0 and extends overthe end of wire member 70. As shown in Figure 8, the end of wire member70 is provided with a substantially V-shaped trough portion into whichthe end 73a of second terminal lead 78 extends. Trough 80 is filled witha fusable metal 82, such as solder, to electrically and mechanicallyconnect second terminal lead 78 to wire member 743.

If desired, body 60 and resistance wire 76 may be provided with aprotective, electrical insulating coating or jacket, leaving theportions of terminal leads 68 and 78 and wire member 70 which projectbeyond body 60 exposed. Although body 60 is shown to be of ellipticalcross-sectional configuration, it may be of any desired cross-sectionalconfiguration, such as rectangular, circular, or the like. Also,although the resistance material is shown to be a metal wire, it canalso be a film of a resistance material, such as carbon or a metal,coated on the surface of body 60 and extending into slots 72 and 74 tocontact terminal lead 68 and wire member 70. Fuse resistor 58 is usedand operates in the same manner as fuse resistor 10 previouslydescribed.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specificatio-n as indicating the scope of theinvention.

I claim:

1. A fuse resistor comprising an electrical resistance element, a bandof an electrically conductive metal secured around said resistanceelement, means electrically connecting one end of said resistanceelement to said band, a terminal member of electrically conductivemetal, means connecting said terminal member to said band, one of saidconnecting means comprising a wire of electrically conductive metal bentback over and extending along said resistance element and releasablysecured to said band by a fusable metal, and a terminal member of anelectrically conductive metal secured to the other end of saidresistance element.

2. The fuse resistor as set forth in claim 1 in which said band isprovided with a substantially U-shaped trough, the open end of whichfaces outwardly away from the resistance element, and the connectingwire extends into said trough and is releasably secured therein by thefusable metal.

3. The fuse resistor as set forth in claim 1 in which said band isprovided with a pair of spaced, substantially parallel arms extendingoutwardly therefrom and a substantially U-shaped trough portion betweensaid arms with the open end of the U facing outwardly away from theresistance element, and the connecting wire extends into said trough andis releasably secured therein by the fusable metal.

4. A fuse resistor comprising a resistor element having an electricallyconducting metal wire terminal lead extending from each end thereof, aband of electrically conducting metal secured around said resistorelement, one of said terminal leads being bent back over and extendingalong said resistor element and releasably secured to said band by afusable metal, and a terminal member secured to said band and extendingbeyond said resistor element.

5. A fuse resistor as set forth in claim 4 in which said band isprovided with a substantially U-shaped trough, the open end of whichfaces outwardly away from the resistor element and the terminal leadextends into said trough and is releasably secured therein by thefusable metal.

6. A fuse resistor as set forth in claim 4 in which said band isprovided with a pair of spaced, substantially parallel arms extendingoutwardly therefrom and a substantially U-shaped trough portion betweensaid arms with the open end of the U facing outwardly away from theresistor element, and the terminal lead extends into said trough and isreleasably secured therein by the fusable metal.

7. A fuse resistor comprising a body of electrical insulating materialhaving a pair of spaced holes extending longitudinally therethrough andslightly beneath the surface thereof, a first terminal member ofelectrically conducting metal fitting into one of said holes andprojecting beyond one end of said body, a transverse slot in said bodyextending from the surface thereof to said one hole to expose a portionof said first terminal member, a second terminal member of electricallyconducting metal fitting into said other hole and projecting beyond bothends of said body, a band of electrically conducting metal securedaround said body, an electrical resistance material on the surface ofsaid body, said resistance material at one end extending into said slotand electrically contacting said first terminal member and at the otherend contacting said band, and one end of said second terminal memberbeing bent back over said body and releasably secured to said band by afusable metal.

8. The fuse resistor as set forth in claim 7 in which said slot islocated adjacent the end of said body from which said first terminalmember extends and the band is located adjacent the other end of saidbody.

9. The fuse resistor as set forth in claim 8 in which said band isprovided with a substantially U-shaped trough, the open end of whichfaces outwardl away from said body and the one end of said secondterminal member extends into said trough and is releasably securedtherein by the fusable metal.

10. The fuse resistor as set forth in claim 8 in which said band isprovided with a pair of spaced, substantially parallel arms extendingoutwardly therefrom and a substantially U-shaped trough portion betweensaid arms with the open end of the U facing outwardly away from saidbody, and the one end of said second terminal member extends into saidtrough and is releasably secured therein by the fusable metal.

11. A fuse resistor comprising an electrical resistance element, a pairof terminal members of electrical conducting metal extending from saidresistance element, one of said terminals being connected to one end ofsaid resistance element, and means connecting the other terminal to theother end of said resistance element, said means including asubstantially resilient member of electrical conductive metal extendingfrom an end of said resistance element and bent back over and extendingalong said resistance element, and a junction of fusable metal at theend of said member over said resistance element.

12. A fuse resistor comprising a body of electrical insulating materialhaving three spaced holes extending longitudinally therethrough, a firstterminal member of electrically conductive metal fitting into one ofsaid holes and projecting beyond an end of said body, a transverse slotin said body extending from the surface of said body to said one hole toexpose a portion of said first terminal member, a member of electricallyconductive metal fitting into a second of said holes and projectingbeyond an end of said body, the projecting end of said metal memberbeing bent back over the body, a second transverse slot in said bodyextending from the surface of said body to said second hole to expose aportion of said metal member, an electrical resistance material on thesurface of said body, said resistance material extending into said slotsand electrically contacting said first terminal member and said metalmember, and a second terminal member of electrically conductive metalextending through the third hole and projecting beyond both ends of saidbody, one of the projecting ends of said second terminal member beingbent back over said body and connected to the end of said metal memberby a fusable metal.

13. The fuse resistor as set forth in claim 12 in which said first andsecond holes in said body are slightly beneath the surface of said bodyand the slots are longitudinally spaced from each other.

14. The fuse resistor as set forth in claim 12 in which the end of saidmetal member which is over the surface of the body has a substantiallyV-shaped trough portion and the end of said second terminal member whichis connected to said metal member fits into said trough portion.

References Cited in the file of this patent UNITED STATES PATENTS1,238,124 Frickey Aug. 28, 1917 FOREIGN PATENTS 931,560 France Feb. 26,1948

